Access speed needs to be fast in a trunking system due to the system's special usages and application sites. Since the paging mode of the traditional CDMA system takes a relatively long time in performing the processes of paging, paging response, then channel assignment, and acquisition, the access speed can not meet the requirement of trunking application. Moreover, the paging of the traditional CDMA system is performed according to the IMSI address, therefore one paging message can only page one terminal, which means serial processing is adopted by the paging terminal. Thus for a group with a lot of users, the time for access would be very long and the requirement for rapid access by the trunking system can not be met. Consequently, only one paging message is needed to page all terminals of the group because all terminals in the group match GID paging address when the Grouping Identifier (GID) paging is applied, and the channel resource is directly carried in the paging message and sent to the terminal while paging the terminals, which largely saves the time for calling and speeds up the access of the terminals.
Grouping calling is usually limited by dispatching area, namely a certain group can call just in a special area (such as an area including several geographically connected cells), and the terminal is not offered with the group call of said group outside the dispatching area. Therefore, the paging message carrying channel resource does not need to be sent in a large area and will not have an impact on the whole system network. In other words, the paging message carrying channel resource is limited to be sent in the given dispatching area, which makes carrying channel resource while paging the terminals possible. For example, a terminal originates a group call, and the paging message carrying channel resource is sent to all cells (always much smaller than the paging area of ordinary CDMA) in the dispatching area of the group, and after the paging message is received by all the group terminals in the dispatching area, the corresponding channel resource is established and the call is accessed.
The above method can realize rapid access of the terminals and is applied in the present CDMA trunking system.
Furthermore, in order to realize the Late-Entry of the terminals, including the terminals switching from power off to power on in the dispatching area and from non-dispatching area to dispatching area, and the re-accesses of the terminals due to an abnormal call drop, the base station side needs to non-periodically or periodically resend the paging message considering that the dispatching system can not monitor the condition of the terminals without accessing the system in real time. The usual solution is that the base station periodically sends the paging message until the calling ends in the process of a group call. Therefore, no matter in which condition, the terminals can receive the paging message in the dispatching area, and based on the received message, it establishes the channel resource and accesses the system with delay.
In the dispatching area, however, if the number of group calls, or the call amount of other services such as voice, data is relatively large, periodically or non-periodically sending the paging message carrying channel resource to realize the Late-Entry of the terminals is a heavy burden for the channel sending paging message, and even may affect the usability of the paging channel, which is a disadvantage of the present paging mode.
To sum up, we need to find a method which can alleviate the impact on the paging channel by the message on the premise that the Late-Entry of the terminals can be met and the normal use of all services is guaranteed.